1. Field of the Invention
The present invention relates to a process for producing a protective-layer-provided substrate by forming a protective layer on a substrate on the surface of which a plurality of structures have been arranged at intervals, and a substrate processing method using the protective-layer-provided substrate.
2. Description of the Related Art
In an ink jet recording apparatus, minute ink droplets are ejected from plural ink ejection orifices arranged in an ink jet head to record an image.
In general, as an ink jet substrate, is used a substrate obtained by forming an ink supply port extending thorough front and back surfaces in a single crystal silicon substrate (hereinafter also referred to as “silicon substrate” merely) cut in the direction of <100> crystal orientation. An ink flows through an ink flow path formed on the ink jet substrate from the ink supply port and flows into an ink chamber in which a pressure-generating element has been formed. An ejection pressure is generated by the pressure-generating element, whereby the ink is flown out of an ink ejection orifice formed in the ink chamber to conduct printing. Incidentally, a member forming a pattern of these ink flow path, ink chamber and ink ejection orifice is generally referred to as an ink jet structure for the sake of convenience. The ink jet structure may be formed of one member or a plurality of members.
The timing of forming the ink supply ports is roughly divided into 2 methods. One is a method of forming an ink jet structure after forming an ink supply port, and the other is a method of forming an ink supply port after forming an ink jet structure. The latter method is required to work and form the ink supply port from the back surface of the substrate because the ink jet structure formed on the front surface of the substrate becomes hindrance.
As methods for forming ink supply ports, have been proposed various methods such as wet etching and laser beam machining. One of such methods is a method of forming it with dry etching. The formation of the ink supply port with the dry etching is required to fix the front surface of the substrate, on which the ink jet structures have been formed, by electrostatic chucking.
However, the surface of the ink jet structure is generally not flat and has projected or dented portions or has unevenness, and a plurality of such ink jet structures may be arranged on a substrate at intervals in some cases. Thus, it may be difficult in some cases to stably fix the ink jet structures by the electrostatic chucking because the ink jet structures themselves each have a large bump or there are voids between the ink jet structures. Incidentally, the thickness of the ink jet structure is known to be generally of the order of 5 to 100 μm.
When the ink jet structure is formed of a material having no conductivity (for example, a resin material), the electrostatic chucking itself may be difficult in some cases because such a material is low in dielectric constant. On the other hand, the electrode voltage upon the electrostatic chucking is set high, whereby chucking becomes feasible. As a result, however, a power source for electrostatic chucking becomes large-sized because a high voltage is required, and discharge may be caused with respect to its surrounding portions in some cases.
Under such circumstances, Japanese Patent Application Laid-Open No. 2002-368071 discloses a structure for easily achieving the electrostatic chucking. Japanese Patent Application Laid-Open No. 2002-368071 describes that a conductive layer (specifically, a conductive film) is formed on a glass substrate difficult to be fixed by electrostatic chucking at low voltages, whereby the substrate can be easily fixed by the electrostatic chucking.
When the technique of Japanese Patent Application Laid-Open No. 2002-368071 is applied to an ink jet substrate on which ink jet structures have been formed, however, the following case may be supposed. More specifically, a void may be present between a film for chucking corresponding to the conductive layer and a bump that the ink jet structure has.
In addition, when a plurality of such ink jet structures are arranged on the surface of a substrate at intervals and a film for chucking is formed, a void may be present between the respective ink jet structures in addition to between the film for chucking and a bump that the ink jet structures each have.
When a substrate 1 on the surface of which a plurality of structures 2 have been arranged at intervals is used as illustrated in FIG. 3, a void 3 may be produced between the respective structures when a film 5 for chucking is formed even when the surface of each structure is a flat surface having no bump. When it is intended to conduct a vacuum process such as dry etching in such a state that such voids are present, the voids may start growing under reduced pressure, resulting in peeling off of the conductive layer (conductive film).
The surface of the ink jet structure is often subjected to a water-repellent treatment, and so the adhesion of the film to the water-repellent surface tends to be more lowered, and the peeling off of the film is liable to occur.
Although the problems on the ink jet substrate have been mentioned above, in substrates on the surfaces of which a plurality of structures have been arranged at intervals, the presence of voids is a common problem.
An object of the present invention is as follows. More specifically, the object is to provide a process for producing a protective-layer-provided substrate that reduces voids produced upon the formation of a film for chucking to reduce the peeling off of the film under reduced pressure and forms smoothness sufficient for stably conducting electrostatic chucking on the surface of the film, and to provide a substrate processing method.